Cell Energy (ATP) Extra Credit Activity Due: Packet and models DUE No later than Wednesday Nov. 4 th at 3:15PM- You must complete ALL parts to get ANY bonus points. Objective: To understand the molecular structure of ATP and ADP. Introduction: Energy in organic molecules exists in the form of chemical energy, and is stored in the chemical bonds. Once the chemical bonds are broken, the energy is released as free energy. A compound called ATP (Adenosine triphosphate) picks up this free energy. When ATP undergoes a decomposition reaction, it loses a phosphate group; it becomes ADP, and releases this free energy to the cell for use in cellular processes. ADP is then converted back to ATP by gaining a phosphate group, a synthesis reaction that requires energy. During a process called cell respiration (to be discussed at a later date), the energy made available from the breakdown of glucose is used to fuel the reaction of synthesizing ATP from ADP. In this investigation, you will: a. use paper models to construct molecules of ATP and ADP b. determine similarities and differences between ATP and ADP c. Illustrate energy release when ATP is changed to ADP d. Study the ATP-ADP cycle Procedure Part A:Examining the Chemical Structure of Adenosine Triphosphate ATP is a nucleotide made up of smaller molecules or subunits- ribose (a 5-carbon sugar), adenine a nitrogen-containing base), and 3 phosphate groups. I. Ribose molecule Examine the structural formula of ribose 1. What is the molecular formula of ribose? (fill in the appropriate subscripts) C H O 2. How does the number of Hydrogen atoms compare to the number of Oxygen atoms in ribose? Ribose is a carbohydrate (a 5-Carbon sugar). It is different from glucose in a very important way. Glucose has 6 atoms of Carbon in each molecule. 3. How many Carbon atoms in ribose? II. Adenine Molecule Examine the structural formula of adenine (a nitrogen base) 1
4. What is the molecular formula of adenine? C H N 5. (a) What element is in adenine that is not in carbohydrates? (b) What element is in a carbohydrate that is not in adenine? (c) What name is used to describe the H-N-H group? (d) Is adenine an amino acid? Why or why not? III. Phosphoric acid (a.k.a. Phosphate group) Examine the structural formula of phosphoric acid. Note: The letter P represents the element phosphorus 6. What is the molecular formula of phosphoric acid? H P O Part B: Constructing an ATP molecule- for this section, you will use the cutouts from page 5 of this packet. There are more cutouts than you need- please discard leftovers. You will need a piece of white or construction paper to glue your models onto. 7. What does the prefix tri- in triphosphate mean? 8. Adenosine is a word made up of a combination of letters from 2 different words. Part of the word comes from ribose (the letters os ). Where do the letters aden and ine come from? Cut out the models of adenine, ribose and phosphoric acid. Attempt to join the adenine and ribose molecules, as you would pieces of a puzzle. 9. What end parts must first be removed from each molecule in order for adenine and ribose to fit together? 10. What molecule is formed from the parts that are removed? 11. What do you call this process? Remove the molecule you named in Question #10. DO NOT THROW THEM AWAY- they are NOT lost!!!! Glue them together on your construction paper. The adenine and ribose molecules can now be chemically joined. New points of attachment or chemical bonds are formed. Glue together the adenine and ribose on your construction paper Examine the phosphoric acid molecules. Attach one of the phosphates to the ribose molecule by removing an H from the phosphate. Glue to construction paper. Attach the remaining phosphates one at a time to the phosphate group already attached to the ribose. Glue to construction paper. 12. What did you remove to make these connections? You have now built an ATP molecule. Please label it. 13. List the 5 molecular building blocks that are needed to make one molecule of ATP: (hint: NOT the atoms, but the actual molecules!) 2
14. What is required for the chemical combination of these parts? Hint: See Introduction) Part C: Gaining energy from ATP as it changes to ADP. Create another molecule, this one with adenine, ribose and only 2 phosphate groups. Glue to construction paper This new compound is called ADP (Adenosine diphosphate). Please label it. 15. What does the prefix di- mean? 16. List the 4 building blocks that are needed to make one molecule of ADP: (hint: NOT the atoms, but the actual molecules!) 17. Explain how an ATP molecule is changed to an ADP molecule: 18. What is released when ATP is changed to ADP? So far, we have seen that ATP can be changed to ADP with energy given off. Energy is required to change ADP to ATP, as this is an endothermic synthesis reaction. Where does this energy come from? See part C for an explanation Part D: An Energy Source for Converting ADP to ATP From where does the energy to form ATP from ADP come from? It does not come from the energy released when ATP changes to ADP. The energy comes from a different source. Energy is stored as chemical energy in the bonds of all organic molecules. Food, such as glucose, contains lots of energy. Glucose is the major source of energy for ATP formation. Energy is released from food during cellular respiration. Examine the structural formula for glucose shown below. In respiration, glucose is broken down into 2 identical molecules of a chemical called pyruvic acid. This step is called glycolysis (glyco = glucose, lysis = break). Glycolysis is the first step in cellular respiration. 19. Count and record the number of chemical bonds in: a. 1 molecule of glucose: b. 2 molecules of pyruvic acid: Note: be sure to count double bonds as 2 bonds (if you can t tell if the diagram is showing a single or double bond, use your knowledge of valence electrons/bonds to determine) 20. Is the amount of energy in 1 glucose molecule the same as the energy in both pyruvic acid molecules? 21. How is some of this extra energy used? Pyruvic acid is broken down further to yield more energy. Energy released from glucose is used in building more molecules of ATP. 3
Analysis Questions: 1. List the name and number of each molecule forming ATP: 2. List the name and number of each molecule forming ADP: 3. How do ATP and ADP differ in: a. # of phosphate groups: b. # of ribose molecules: c. # of adenine molecules: d. amount of potential chemical energy: 4
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